Insect pests such as, for example, leafrollers, tomato pinworms, oriental fruit moths, and codling moths can cause significant damage and economic loss in the production of tree fruits, vine and nut crops, and various other crops. In the past, such insect pests were typically controlled with pesticides such as, for example, organophosphate pesticides. Due to regulatory and environmental pressures, however, insect pest control is moving away from exclusive reliance on pesticides. As a result, alternative crop protection strategies such as insect mating disruption technology have steadily increased in general acceptance.
Insect mating disruption is an important component of the modern approach to pest regulation known as integrated pest management, which combines biological, cultural, physical, and chemical techniques to regulate pest populations while minimizing cost and environmental disturbances. The typical mating disruption technique confuses male insects with pheromones from the natural chemical blends of conspecific females. Sources of sex pheromone are placed in a crop or environment at concentrations sufficient to mask the presence of females. Decreasing or delaying the mating of the moths thus decreases the population of the next generation of larva, as well as the potential for future crop or environmental damage.
It is often difficult, however, to economically manufacture pheromone compounds for use in mating disruption techniques. Many methods for preparing pheromone compounds require complex multi-step sequences to arrive at the target compound (see, for example, Vincer et al., Acta Chim. Hung., 124, 737 (1987); WO 94/17662; and JP 3240752), or rely upon starting materials such as, for example, cis-alkenyl chlorides that are not readily available and necessitate preparation by multi-step processes (see, for example, EP 0 038 052 B1). Other methods yield only modest results such as, for example, less than 50% yield (see, for example Kang et al., Bull. Korean Chem. Soc. 7(6), 453 (1986)).
Also, in order for mating disruption techniques to be effective, synthetically prepared pheromones must closely mimic those naturally produced by insects. Natural insect pheromones are typically blends of stereoisomers. There is a very specific tuning of the isomeric blends in the pheromones released by insects. This tuning provides species specificity and proper biological effect. Minor alterations of the isomeric blends can inhibit the pheromonal effect. When preparing pheromone compounds, however, it is often difficult to control the stereoselectivity of the forming double bond to yield the desired stereoisomer.